The present disclosure relates to a magnetic resonance force detection apparatus, and associated methods for using such apparatus.
Magnetic resonance force microscopy (MRFM) involves the combination of magnetic resonance imaging (MRI) with the techniques of scanning probe microscopy (SPM). Essentially, the technique relies on detecting the tiny force resulting from the modulation or flipping of nuclear or electron spins. Recently this has led to the demonstration of nuclear spin imaging of a virus particle with a spatial resolution of 4 nm. Most recently, the sensitivity has been improved by increasing the magnetic field gradient provided by an integrated nanomagnetic tip near the nuclear spins and a “microwire” RF source. Yet, because of the small forces involved, relatively long averaging times are required to be able to distinguish the forces due to the controlled manipulation of the nuclear spins from the thermal forces acting on a cantilever that is used for force detection.
U.S. Pat. No. 5,266,896 describes using a mechanical cantilever to detect the modulation of nuclear or electron spin magnetism in a sample where a high frequency magnetic field is used to drive spin resonance and thereby control the modulation or reversal of the spins in the sample.
The paper entitled “Nanoscale Magnetic Resonance Imaging” by C. L. Degen, M. Poggio, H. J. Mamin, C. T. Rettner and D. Rugar, dated 11 Nov. 2008 and published in the PNAS (Proceedings National Academy of Sciences) journal, describes converting measured magnetic force data into a three-dimensional map of nuclear spin density, taking advantage of the unique characteristics of the “resonant slice” that is projected outwards from a nanoscale magnetic tip. Since the field from the magnetic tip is a strong function of position, the resonance is confined to a thin, approximately hemispherical “resonant slice” that extends outwards from the tip. The field gradient at the resonant slice can exceed 4×106 T/m at a distance of 25 nm from the tip, resulting in a slice thickness that is as thin as a few nanometers. The spin signal is measured as the magnetic tip is mechanically scanned with respect to the sample in a three-dimensional raster pattern, yielding a map of the spin signal as a function of tip position.
The paper entitled “Fast magnetic resonance force microscopy with Hadamard encoding” by Kai W. Eberhardt, Christian L. Degen, and Beat H. Meier dated 26 Nov. 2007 (PHYSICAL REVIEW B 76, 180405(R) (2007)) discloses a spatial encoding technique for magnetic resonance force microscopy that allows for a much enhanced image acquisition rate. The technique uses multiplexing, based on spatial Hadamard encoding, to acquire several slices of the image simultaneously and at an undiminished signal-to-noise ratio.
The listing or discussion of a prior-published document or any background in this specification should not necessarily be taken as an acknowledgement that the document or background is part of the state of the art or is common general knowledge. One or more aspects/embodiments of the present disclosure may or may not address one or more of the background issues.